1. Field of the Invention
The present invention relates to an anti-reflection microstructure having a function for preventing light reflection, to an anti-reflection mold body which includes the anti-reflection microstructure and is suitable for applications as a non-reflective panel for various meters, display devices, etc. to be installed in a vehicle such as an automobile, a ship, or an airplane, and further to a method of manufacturing the anti-reflection mold body.
2. Description of the Related Art
When outside light or room illumination is projected on a screen of a display device such as a liquid crystal display or a CRT display, for example, on a household television screen, visibility of screen images is substantially deteriorated.
In an automobile, a display unit accommodating a variety of indicators such as a speedometer or a fuel gauge is provided in front of a driver's seat. The display unit has a meter front cover fitted to the front thereof. If outside scenes are projected onto the meter front cover through a front windshield or a side windshield, it becomes hard to read the indicators on the display unit. Usually, a meter hood is provided above the meter front cover so as to prevent the projection of outside light onto the cover.
As a typical anti-reflection mold body for preventing the light reflection as described above, a multilayer anti-reflection film made of multiple thin films with mutually different refractive indices is conceived.
Moreover, Japanese Patent Application Laid-open Publication No. 2002-267815 discloses an anti-reflection mold body including a microstructure which has lower reflection rate than such a multilayer anti-reflection film.
This anti-reflection mold body is a transparent formed product having on a surface thereof numerous fine convex portions to change refractive index continuously in the thickness direction thereof. The convex portions are made of a transparent material and formed at a pitch of not exceeding a wavelength of light.
Specifically, the anti-reflection mold body has on the surface thereof a layer of numerous fine convex portions in wave shapes or triangular shapes. Since percentage of the transparent material of the fine convex portions is infinitely close to 0% at the outermost region of the asperity layer, the refractive index therein is virtually equal to a refractive index of air (1.0). Meanwhile, since percentage of air is infinitely close to 0% at the innermost region of the asperity layer, the refractive index therein is virtually equal to a refractive index of the transparent material. Moreover, in an intermediate region of the asperity layer, the refractive index varies within a range from the refractive index of air to the refractive index of the transparent material depending on the percentage of the transparent material or the air at the region.
The anti-reflection mold body thus has the refractive index changing continuously in the thickness direction thereof, which provides the mold body with a superior anti-reflection function to the multilayer anti-reflection film which is formed of stacked thin films having different refractive indices and has the refractive index changing stepwise in the thickness direction thereof.